Veltassa Vs Kayexalate: Comparison of Potassium-Lowering Drugs

Veltassa Vs Kayexalate

Veltassa and Kayexalate are both resins that bind with potassium in the gut and prevent the absorption of dietary potassium into the bloodstream.

Until the last few years, Kayexalate was the only resin available. Over the last few years, new potassium-binding resins have been approved which are considered safer than kayexalate and may be more effective as well.

Here is a list of the FDA-approved potassium exchange resins:

Potassium exchange resins

FDA-approval dates

KayexalateNot specified
Patiromer21st October 2015
Sodium Zirconium Cyclosilicate18th May 2018


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Veltassa Vs Kayexalate:

Veltassa is the brand name of Patiromer. It is manufactured by Relypsa Pharmaceuticals and approved by the FDA for the treatment of hyperkalemia in 2015.

Kayexalate, on the other hand, has been in the market for many years. It is probably been used since 1950.

There are subtle differences between the mechanisms, efficacy, and side effects of Veltassa and Kayexalate. These differences are discussed below:

  • Veltassa is more specific than Kayexalate:

The active ingredient of Veltassa is Patiromer Sorbitex Calcium. It specifically binds with Potassium in the diet in exchange for Calcium ions. In the colon, it also binds with Magnesium and may also lower plasma Magnesium levels. Veltassa, therefore, causes hypokalemia and hypomagnesemia.

On the other hand, Kayexalate is the brand name of Sodium Polystyrene Sulfonate (SPS). It binds with dietary Potassium in exchange for Sodium ions.

However, it also binds with Calcium and Magnesium and may cause severe Hypomagnesemia and Hypocalcemia. In addition, the Sodium in Kayexalate may cause fluid overload, especially in patients with heart failure and hypertension.

  • Kayexalate has a relatively rapid onset of action but a more frequent dosing schedule:

The onset of action of Kayexalate is about 2 hours. It may vary but is typically between hours to days. It is administered every 6 to 8 hours depending on the severity of Hyperkalemia.

Patiromer (Veltassa) on the other hand, has a slow onset of action of about 7 hours compared to 2 hours of Kayexalate. It is usually administered once daily.

Where rapid removal of potassium is needed, Kayexalate may be preferred. However, for long-term use as in patients with chronic hyperkalemia, Veltassa may be preferred because of the ease of administration.

  • Veltassa has fewer drug interactions than Kayexalate

Kayexalate binds to many substances other than potassium. It binds to many drugs that are taken orally. The FDA issued a warning to healthcare providers in 2015 about the potential drug interactions between Kayexalate and orally administered drugs [Ref].

Specifically, the FDA pointed to a study in which the following drugs were given with Kayexalate:

  • Amlodipine
  • Metoprolol
  • Amoxicillin
  • Furosemide
  • Phenytoin
  • Warfarin

Because the drugs included in the study were taken from various classes including blood pressure-lowering medicines, antibiotics, seizure medicines, drugs used to treat heart failure, and blood thinners, the FDA recommended spacing Kayexalate and all other medicines by 3 hours.

It is therefore recommended to give oral medicines at least three hours before or three hours after administering Kayexalate.

This time interval should be increased to six hours in individuals who have gastroparesis such as diabetics or those on medications that lower gut motility like GLP-1 analogs (Ozempic, Victoza, Trulicity) and Mounjaro (Tirzepatide).

In contrast to Kayexalate, Veltassa has fewer drug interactions. Because it is a resin that can bind to drugs (similar to Kayexalate), the manufacturer recommends avoiding it with concomitant oral medicines, especially life-saving medicines such as antibiotics like Ciprofloxacin, antidiabetics (metformin), and Levothyroxine.

The manufacturer recommends a time interval between oral medication and Veltassa to be at least 6 hours. Although this is longer than Kayexalate, it is more feasible because Veltassa is administered once daily.

  • Veltassa has fewer side effects compared to Kayexalate

One of the main advantages of Veltassa is its safety compared to Kayexalate. Veltassa is associated with fewer side effects compared with Kayexalate.

In addition, more studies have been carried out on Veltassa use in Pregnancy and hence, it is labeled as a “Category B Drug in Pregnancy” while Kayexalate is labeled as a “Category C Drug in Pregnancy”.

The table below compares the contraindications and side effects of Veltassa and Kayexalate:

Side effects



  • Allergic reactions
  • Hypokalemia
  • Allergic reactions
  • Hypokalemia
  • Intestinal Obstruction
  • Use in neonates with lower GI motility and oral administration in neonates
Serious side effects
  • Impairs the absorption of other life-saving oral medications
  • May not be effective and worsen the underlying GI condition in patients with GI motility disorder, severe constipation, bowel obstruction, and inflammation (as in IBDs)
  • Hypomagnesemia
  • Impairs the absorption of most oral medications
  • Colonic necrosis is one of the most dreaded side effects of Kayexalate which may result in bleeding, ischemic colitis, or gut perforation)
  • Severe hypomagnesemia, hypocalcemia, and hypernatremia
  • Seizures can occur in patients who are given kayexalate with magnesium hydroxide laxatives
  • Worsening hypertension, Heart failure, and fluid overload can occur as a result of sodium retention
Other side effects
  • Constipation
  • Diarrhea
  • Abdominal pain
  • Abdominal gases
  • Bloating
  • Nausea
  • Hypomagnesemia
  • Hypokalemia
  • Constipation
  • Diarrhea
  • Abdominal pain
  • Abdominal gases
  • Bloating
  • Nausea and vomiting
  • Hypernatremia
  • Hypocalcemia
  • Hypomagnesemia
  • Hypokalemia
  • Veltassa is more effective than Kayexalate:

Data about the efficacy of Kayexalate in patients with hyperkalemia is limited. It is generally said that for 1 mg of potassium in the diet, you need 1 gm of Kayexalate resin. The average daily potassium intake of a normal person is between 2000 to 3000 mg. 90% of this potassium gets absorbed.

Thus when administered in a dose of 15 gm every six hours, it is going to create a negative potassium balance of only 60 gm per day.

Whether this calculation correctly describes the potassium balance is not validated. Hence, frequent monitoring is required unless the serum potassium is brought down to normal.

The efficacy of Veltassa has been studied in trials. In a trial of 243 patients, Veltassa brought down potassium by -0.65 mEq in patients with baseline potassium ranging from 5.1 to 5.5 mEq/L.

For those with baseline potassium of 5.5 to 6.5 mEq/L, Veltassa brought down potassium by -1.23 mEq/L in 4 weeks [Ref].

  • Kayexalate is widely available and may be Cheaper than Veltassa

In the United States, the average cost of Kayexalate powder is about $800 USD for a total of about 450 gm of Kayexalate.

The average cost of 4 Sachet of Veltassa, 8.4 gm, in the United States is about $195 USD.

Thus, the average daily cost of Kayexalate is $106 USD if given in a dose of 15 gm every 6 hourly while the average daily cost of Veltassa is $48.75 USD if given once daily and $146.25 USD if given in the maximum dose of 25.2 gm per day.

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In Conclusion:




Drug NamePatiromer Sorbitex CalciumSodium Polystyrene Sulfonate
FDA Approved21st October 20151958
Onset of action7 hours2 hours
Dosing frequencyOnce daily3 to 4 times a day
Drug InteractionsYes but fewer than SPSYes
Side effectsFewer side effectsMore side effects
EffectivenessProved in trialsLimited data
AvailabilityNot available everywhereWidely available
CostMay be more costlyCheaper
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What do you think?

Written by Dr. Ahmed

I am Dr. Ahmed (MBBS; FCPS Medicine), an Internist and a practicing physician. I am in the medical field for over fifteen years working in one of the busiest hospitals and writing medical posts for over 5 years.

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